System for ground speed determination



Feb. 7, 1950 Filed Feb. 2, 1946 COMPUTER DATA TRANSFORMED T0 X AND Y COORUINATES A. C. OMBERG SYSTEM FOR GROUND SPEED DETERMINATION INFORMATION SOURCE TWO AUTOMATIC DIRECTION FINDERS AND FLUX GATE COMPASS, OR ONE DIRECTION FINDER AND RADAR RANGE, ETC.

FTEIS gwvvwto b ARTHUR C. OMBERG Patented Feb. 7, 1950 SYSTEM FOR GROUND SPEED DETERMINATION Arthur 0'. Ombe'rg, Owings Mills, Md., assignor to Bendix Aviation Corporation, Towson, Md., a

corporation of Delaware Application February 2, 1946, Serial No. 645,160

1 Claim.

This invention relates to systems for the deterinitiation of the ground speed of air orwater borne vehicles, :and more particularly to such systems which generate voltages proportional to the components of the ground speed of the vehicle along mutually perpendicular direction lines and combine these voltages vectorially to derive a resultant ground speed.

In the navigation of such vehicles it is highly desirable that the navigator have readily available information. as to the speed actually being made good over the ground, in order that progress to a destination may be checked, time of arrival at the destination be accurately estimated and steps taken to correct deviations from a desired rate of progress. In order that human errors may be minimized, crew personnel be reduced to a minimum and information be quickly available for use, it is desirable that some means be provided for automatically, quickly :and accurately furnishing the desired information.

It is an object of this invention to provide a method and means for continuously and accurately determining and indicating the ground speed of an air or water borne vehicle. I

It is another object of this invention to provide a method and means for deriving the ground speed of the vehicle from information as to the components of the ground speed of the vehicle along mutually perpendicular direction lines.

It is a further object of the invention to provide a method and means for continuousl determining from information as to the position orthe vehicle with respect to one or more known points in an area being traversed, the rectangular coordinates of said position, and deriving from said coordinates the ground speed of the vessel.

It is still another object of the invention to generate voltages proportional to the components of the ground speed of the vehicle along mutually perpendicular direction lines and toderive from those voltages the ground speed of the vessel.

The objects and advantages of the invention are attained by means computing from information as to the position of a vehicle with respect to one or more known stations, the rectangular coordinates of the vehicle's position, generating voltages proportional to the rate of movement of the vehicle alone directions indicated by said-coordinates, electrically squaringand combiningthose voltages and indicating the resultant in terms of its square root.

- Other objects and advantages of the invention will become apparent from a consideration of the following specifications when taken in conjunction with the accompanying drawing, in which:

Fig. 1 is a schematic diagram of a system embodying the invention;

Fig.2 is a schematic diagram of a modified portion of the system of Fig. 1, and;

Fig. 3 is a front elevational view of a dial forming a part of the systems of Figs. 1 and 2.

Referring now more particularly to Fig. 1 of the drawing, the block I indicates a source of information as to the position of the vehicle relative to one or more points of known location. The source may include, for example, two automatic radio direction finders providing bearings of the points and a flux gate compass providing information as to the vehicles heading. Or it may consist of one automatic direction finder and a distance determining device such, for example, as a'pulse echo system; Other combinations of information providing devices may be used, a pair of echo ranging devices providing distances to a plurality of points of known location, or navigational devices providing information as to the difference between the distances to such points.

The information supplied by the source I is applied to computer '2 which converts it into voltages proportional to the rectangular coordinates of the position of the vehicle upon a chart 2| of the area being traversed. In so doing the information is applied to the computer and the output information is derived in terms of an arbitrary voltage-distance scale.

The voltage proportional to the X coordinate, as computed, is applied to a motor 4 which drives a lead screw 1 extending parallel to and spanning the horizontal dimension of the chart 2|. Supported on'and driven by the lead screw 1 is a cursor 23 carrying a motor 6 which drives a lead screw 8 extending parallel to and spanning the vertical dimension-of the chart. The lead screw 8 drives a cursor I l carrying a stylus which travels over the chart 2! to mark the location of the ometer 25. The cursor supporting motor 6 carries a sliding contact I! and the cursor II carries a sliding contact I9, which contacts travel along the respective potentiometers 9 'and 25. An arbitrary voltage is applied to the potentiometers, the value of the voltage being in proportion to the chart distance spanned by the potentiometers in terms of the selected voltage-distance scale.

The voltage proportional to the Y coordinate, as developed by the computer 2 is applied to motor 6. The potentials intercepted by the sliding contacts I1 and I9 along the potentiometer-s are fed back to the computer to reduce, the X and Y voltages applied to the motors 4 and 6 as th cursor II nears the correct position.

Accordingly, if the vessel is in continuous m0? tion the resultant voltages fed to'the motors4 and 6 and the rotation of lead screws 1 and 8 will The portion of the system described thus far will be found described more 'fully' and ingreater detail in my copending application for Automatic position plotter, Serial No. 642,969, filed January :23, 1946. v

In order to determine the resultant ground speed from these components it is necessary to combine them vectorially. The invention contemplates the accomplishment of this result by electrical means, two arrangements for this purpose being illustrated in Figs. 1 and 2.

In the embodiment of Fig. 1 the motor 4 drives a direct or alternating current generator III through lead screw I. drives a direct oralternating current generator 44 through lead screw 8.

The generator Ill is connected to a heater element I2. This element I2 heats the adjacent junction I8 of a thermocouple 20. Likewise, the generator I4 is connected to a heater element l6, which heats the junction 22 of a thermocouple 24. The positive terminal 26 of thermocouple is connected to the negative terminal 28 of thermocouple 24 by series connection of the thermoelements, and the remaining terminals 30 and 32 of the two thermocouples are connected to a metering device 34.

The heat generated in a heater element by the application of a voltage thereto is proportional to the square of the applied voltage. Thus, :if E1 is the voltage developed by the power source IIG across the heater element I2, the heat generated in heater element I2 will be proportional to E1 Likewise, if the power source I4 develops ;a voltage E2 across the heater element IS, the heat generated in heater element I6 is proportional to E2 Heater element I2 raises the temperature of. junction I8 of thermocouple 20, and heater element l6 similarly raises the temperature of junction 22 of thermocouple 24. The electromotive force generated in each thermocouple is proportional to the heat supplied to each junction. Therefore, the E'. M. F. developed by thermocouple 26 is proportional to E1 and the E. IVE. F- developed by thermocouple 24 proportional to E2 The E. M. F. of the series-connected thermocouples 26 and 24 and the E. M. F. applied to the metering device 34 is therefore proportional to (E1 +E2 A reduction in heater input voltage will reduce the temperature thereof, but due to the thermal inertia of such devices, temporary variations of voltage input due to hunting of the motors 4 and 6 will be averaged out, the thermo-- The motor 6 likewise Circuits in series. and 62of the two rectifier circuits 36 and 33 are 4 of the average input over a small period of time.

In the modification of the system of Fig. 1 illustrated in Fig. 2 and constituting a second embodiment of the invention, generator I0 supplies power to a copper-oxide rectifier 40 through a resistance 44 and to a copper-oxide rectifier 42 through a resistance 46. The two rectifiers 40 and 42 are series-connected and form the rectifier circuit 36. Generator l4 supplies power to a copper-oxide rectifier 48 through a resistance 52, and to a copper-oxide rectifier 50 through a resistance 54. The two rectifiers 48 and 5!] are series-connected and form the rectifiercircuit 38. The electrically oppositely polarized terminals 56 and 58 of the two rectifier circuits 36 and 38 are connected together thus connecting the rectifier The remaining terminals 60 -;.connected to the. terminals 64 and 66 of the metering device 34. In this embodiment the generators l0=and I4 are of the alternating current variety.

The output voltage of a rectifier circuit of the kind used in this apparatus is a function of the input voltage and the connected resistance. This resistance can. be so chosen, that, within the voltage range to be considered, the output voltage of the rectifier circuit is proportional to the square of the input voltage. Generator I0 supplies a voltageEi .to the rectifier circuitv 36,,in which the two rectifiers '40 and 42 are series-connected in orderto more nearly approach the desired linearity voltage output which should be proportional to the square of the input. Through proper choice of the resistors 44 and 46, the rectifier circuitwilliprovide an output Voltage proportional to E1 Generator I4 supplies the voltage new the rectifier circuit 38, and through proper selection of the resistors 52 and 54 rectifier circuit 38 will develop an output voltage proportional t0'E2 "The rectifier circuits 36 and 38 are seriesconnected. Together they supply a voltage proportional to (Ei -I-E2 to the metering device 34.

- In'Figure 3 there is shown the dial 68 of the metering device 34 provided with a pointer Ill and a scale 12. It is calibrated in the square roots of the values which would be indicated under con- .sideration of the constants of proportionality which relate the original quantities to be added vectorially to the movement of the pointer 10 of the metering device. If connected as indicated to'the circuits described in Figures 1 and 2, the pointer will read the resultant of the two original velocity vector s'represented by the voltages generated by the generators I0 and I4. This resultant represents the resultant velocity or ground speed of the vehicle.

Even though the disclosure has been limited 'to a showing of the derivation of ground speed from voltages proportional to the components of the groundspeed of the Vessel along east-west and north-south lines, it will be apparent that -falling within the scope of the appended claim will occur to those skilled in the art. It is therefore to be understood that the scope of the inventionis not to be considered aslimited to the emcouple output being proportional to the square Wlbodiments disclosedherein," 5 I ing device indicating the square root of the volt- 15 Number age measured by it.

ARTHUR C. OMBERG.

REFERENCES CITED The following references are of record in the file of this patent:

5 UNITED STATES PATENTS Number Name Date 2,080,186 Reymond Mar. 11, 1937 2,314,764 Brown Mar. 23, 1943 10 2,404,387 Lovell July 23, 1946 2,410,707 Bradley et a1. Nov. 5, 1946 2,438,112 Darlington Mar, 23, 1948 FOREIGN PATENTS Country Date 633,493 Germany Aug. 3, 1936 499,239 Great Britain Jan. 20, 1939 

